FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/phy/rockchip-emmc-phy.txt

     Rockchip EMMC PHY
     -----------------------
     
     Required properties:
      - compatible: rockchip,rk3399-emmc-phy
      - #phy-cells: must be 0
      - reg: PHY register address offset and length in "general
        register files"
     
    Optional properties:
     - clock-names: Should contain "emmcclk".  Although this is listed as optional
                    (because most boards can get basic functionality without having
                    access to it), it is strongly suggested.
                    See ../clock/clock-bindings.txt for details.
     - clocks: Should have a phandle to the card clock exported by the SDHCI driver.
     - drive-impedance-ohm: Specifies the drive impedance in Ohm.
                            Possible values are 33, 40, 50, 66 and 100.
                            If not set, the default value of 50 will be applied.
     - rockchip,enable-strobe-pulldown: Enable internal pull-down for the strobe
                                        line.  If not set, pull-down is not used.
     - rockchip,output-tapdelay-select: Specifies the phyctrl_otapdlysec register.
                                        If not set, the register defaults to 0x4.
                                        Maximum value 0xf.
    
    Example:
    
    
    grf: syscon@ff770000 {
            compatible = "rockchip,rk3399-grf", "syscon", "simple-mfd";
            #address-cells = <1>;
            #size-cells = <1>;
    
    ...
    
            emmcphy: phy@f780 {
                    compatible = "rockchip,rk3399-emmc-phy";
                    reg = <0xf780 0x20>;
                    clocks = <&sdhci>;
                    clock-names = "emmcclk";
                    drive-impedance-ohm = <50>;
                    #phy-cells = <0>;
            };
    };

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